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The blood flow dynamics of a stenosed, subject-specific, carotid bifurcation are numerically simulated using Reynolds-averaged Navier–Stokes (RANS) turbulence models and direct numerical simulation (DNS). The latter is taken as a term of comparison for the RANS calculations, which include classic two-equations eddy-viscosity models (k - epsilon, k - omega) as well as a transitional three-equation model (kT - kL - omega). Pulsatile inlet conditions are based on in vivo ultrasound measurements of blood velocity, the blood is modelled as a Newtonian fluid and the vessel walls are considered rigid.
The main purpose of this work is to highlight the problems which arise when classic RANS models are employed in the numerical simulation of such flows. Moreover, the capabilities of the transitional three-equation model for this specific case are assessed through a comparison between the DNS and the RANS simulations.
The results demonstrate that the three-equation eddy-viscosity model better predicts the flow in terms of turbulence intensity, pressure temporal evolution and oscillatory shear index (OSI). The DNS points out the transitional or weakly turbulent state of the blood flow, which features velocity and pressure fluctuations in the post-stenotic region of the internal carotid artery (ICA) during systole and laminar flow during di- astole.